An Evidence for Remarkable Difference of the Electrophilicity between Two Carbonyl Groups in the Photoexcited 1,2-Naphthoquinone. Photocycloaddition Reaction of 1,2-Naphthoquinone with Olefins

Abstract The [4+2]photocycloaddition reactions between 1,2-naphthoquinone and olefins have been investigated. From the results of the stereochemistry and the regiochemistry of the adducts, it is concluded that the carbonyl oxygen atom at the position 2 in the photoexcited triplet state of 1,2-naphthoquinone attacks selectively one of the olefinic carbons.